This invention relates to an analog multiplexer capable of selectively producing one among a plurality of analog signals.
In a prior art analog multiplexer, for example, the sources of a plurality of MOS transistors are connected with one another, the drains of the transistors are supplied with varied analog signals as input signals, and a control signal is supplied to the gate of one of those MOS transistors, whereby the analog voltage supplied to the drain of such transistor is obtained at the source side. That is, an MOS transistor with its drain supplied with a desired analog signal is caused to conduct to derive a potential from the drain to the source of the MOS transistor, thereby ensuring the function of the analog multiplexer. The conduction resistance of the MOS transistor in conduction varies from approximately 100.OMEGA. to 1 k.OMEGA. depending on the elements. Therefore, in such conventional analog multiplexer, the conduction resistance of the MOS transistor causes a voltage drop in the analog signal to enlarge the difference between the input and output signals, thereby reducing the accuracy. Further, the circuit construction is relatively complicated, while the response of the output to the input is slow.